Northern CSO
Storm overflow operated by United Utilities. The source names The Mersey Estuary as the receiving water.
- 20
- Spills in 2025
- 39.1
- Recorded hours
- 100%
- Monitor operation
- 2
- Years listed
The reported spill count was 17 lower than in 2024. This compares event counts, not discharge volume.
Checking the latest monitor report…
How it compares in 2025
Northern CSO recorded 20 spills in 2025. That is more than 63% of the 14,239 overflows in England with a reported figure, and ranks 5,045th nationally. Among United Utilities overflows it ranks 1,007th of 2,270; the median United Utilities overflow recorded 15 spills. On the MERSEY - Transitional waterbody it ranks 36th of 78.
| Group | Rank by spills | Median spills | Median hours |
|---|---|---|---|
| This outlet | – | 20 | 39.1 |
| England | 5,045th of 14,239 | 11 | 22.3 |
| United Utilities | 1,007th of 2,270 | 15 | 29.1 |
| MERSEY - Transitional | 36th of 78 | 15 | 34.5 |
Rank 1 has the most spills. Equal counts share a rank. Only overflows with a reported count are ranked. Counts do not measure volume, so a higher rank does not mean more sewage.
Annual spill history
| Year | Spills | Duration | Monitor operation | Source |
|---|---|---|---|---|
| 2025 | 20 | 39.1 hours | 100% | Official data |
| 2024 | 37 | 53.6 hours | 100% | Official data |
A missing figure means the source did not provide a usable value. A zero is shown as zero. Monitor operation below 90% can make comparison less reliable.
Outlet details
- Water company
- United Utilities
- Outlet type
- Storm overflow on the sewer network
- Permit
- 016830968
- Activity reference
- A1
- Grid reference
- SJ3300093900
- Waterbody ID
- GB531206908100Official waterbody record ↗
- Location source
- Official annual grid reference
- Location precision
- About 1 metres
- Location note
- Unknown
About the name and type
The annual return lists this asset as “SO on sewer network”: storm overflow on the sewer network. The return places this overflow on the sewer network.
The waterbody link opens the Environment Agency record for the exact ID in the return. It is a source lookup; we do not import its classification.
Where it is
The recorded position is about 2.3 km south-west of the Bootle (Sefton) reference point in the ONS built-up areas data.
Designated bathing waters within 3 km in a straight line:
Distance does not show that water from this outlet reaches a bathing water. Check the official bathing-water profile for its classification and advice.
Area and water pages
Check the official record
Public access to this outlet is unknown. Do not enter restricted land or use this page as a route guide.
Open official source ↗Other outlet records nearby
- Bankhall Relief CSOCurrent status unknown
United Utilities · River Mersey Estuary
- Bankhall CSOCurrent status unknown
United Utilities · Mersey Estuary
- Millers Bridge CSOCurrent status unknown
United Utilities · Mersey Estuary
- Strand Road CSOCurrent status unknown
United Utilities · River Mersey
Questions about Northern CSO
- Who operates Northern CSO?
- United Utilities is the operator named in the annual record. The permit reference is 016830968.
- Where does Northern CSO discharge?
- The source names The Mersey Estuary as the receiving water. This does not show how far a discharge travelled.
- How many times did Northern CSO spill in 2025?
- The 2025 return records 20 counted spill events and 39.1 hours of recorded discharge. Spills are counted with the 12/24-hour method, so this is not a count of every start signal.
- Can I trust the 2025 figures for this outlet?
- The monitor worked for 100% of the reporting period, so the annual figures cover most of the year. They still do not measure discharge volume.
- Is Northern CSO discharging right now?
- This record is linked to a company live feed. The panel above shows the latest report we hold, with its date. That report can be old, and the monitor can be offline, so check the date before relying on it. A report that no discharge is taking place is not a water-quality result.
- How accurate is the map marker?
- The marker comes from the grid reference in the official annual return, which is accurate to about 1 metres. It shows the recorded outlet position, not the extent of any discharge.
- What kind of outlet is Northern CSO?
- The annual return lists the asset type as “SO on sewer network”, which means storm overflow on the sewer network. The return places this overflow on the sewer network.
- How does Northern CSO compare with other overflows?
- Northern CSO recorded 20 spills in 2025. That is more than 63% of the 14,239 overflows in England with a reported figure, and ranks 5,045th nationally. Among United Utilities overflows it ranks 1,007th of 2,270; the median United Utilities overflow recorded 15 spills. On the MERSEY - Transitional waterbody it ranks 36th of 78. Ranks compare counted spill events only. They do not compare volume or harm.
- Does zero spills mean the water was safe?
- No. A zero means the annual return recorded zero counted spill events for this outlet and year. It is not a water-quality test, and pollution can come from other sources.